From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: sync guest calls made async on host - SQLite performance Date: Sun, 11 Oct 2009 11:16:42 +0200 Message-ID: <4AD1A27A.4060307@redhat.com> References: <4ABC6AA5.6080909@tauceti.net> <4AC259DC.2080807@codemonkey.ws> <4AC260BB.3090906@gmail.com> <4AC27355.3090303@codemonkey.ws> <4ACCC7A1.9060303@gmail.com> <4ACCEC9F.7090309@gmail.com> <4ACE0196.9010904@gmail.com> <4ACF89CB.5020406@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Dustin Kirkland , Anthony Liguori , RW , kvm@vger.kernel.org, Christoph Hellwig To: Matthew Tippett Return-path: Received: from mx1.redhat.com ([209.132.183.28]:58649 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755076AbZJKJRW (ORCPT ); Sun, 11 Oct 2009 05:17:22 -0400 In-Reply-To: <4ACF89CB.5020406@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On 10/09/2009 09:06 PM, Matthew Tippett wrote: > Thanks Duncan for reproducing the behavior outside myself and Phoronix. > > I dug deeper into the actual syscalls being made by sqlite. The > salient part of the behaviour is small sequential writes followed by a > fdatasync (effectively a metadata-free fsync). > > As Dustin indicates, > > if scsi is used, you incur the cost of virtualization, > if virtio is used, your guests fsyncs incur less cost. > > So back to the question to the kvm team. It appears that with the > stock KVM setup customers who need higher data integrity (through > fsync) should steer away from virtio for the moment. > > Is that assessment correct? > Christoph, wasn't there a bug where the guest didn't wait for requests in response to a barrier request? -- error compiling committee.c: too many arguments to function